The Moon travels around the Earth in what is about a 28 day cycle, a lunar month. Depending on its position relative to the Sun, the Moon appears to Eathlings in different shapes. A New Moon hides directly behind the Earth, not reflecting the Sun’s light, so it is not visible from Earth. In the early part of the cycle, the Moon appears as a crescent, getting slightly bigger each night; this is called a Waxing Moon. Halfway through the cycle, following the full Moon, it begins getting slimmer each night (a Waning Moon).

Most months are 30 or 31 days long. So, every once in a while, a Full Moon occurs twice in the same month. This is referred to as a Blue Moon.

Tonight — July 31, 2015 – we will see a Blue Moon. The next one will occur on January 31, 2018